It seems a fitting topic of discussion for a blog about the Post-Apocalypse, although this is a particularly old one. And it got better.
But why did it happen?
You don't need to read Gibbon's Decline and Fall of the Roman Empire to find out; this blog post reduces it to six easily digestible points. How's that for brevity?
Of course, anyone and everyone interested in history eventually stumbles across this question, and the answers are as plentiful as they are.
Every ideological agenda has an explanation to fit, ranging from Marxist to Libertarian. Some say it never happened at all, that the empire just morphed into a different form.
Theories wax and wane. Historians, believe it or not, follow trends.
Here's what Matthew White has to say about it:
"…There is also a tendency to downplay the violence associated with barbarian invasions—as well as frowning on calling them barbarians. In fact, some scholars argue that the whole fall of the Western Roman Empire is overrated as a milestone, and that the changes sweeping Europe were mostly the peaceful immigration of wandering tribes, who imposed a new ruling class but were culturally assimilated in a couple of generations.
This view is especially popular among the English, Americans, and Germans since they are the descendants of the aforementioned barbarians, who would now seem less barbaric… Every now and then scholars grow bored with overrated golden ages, and they gain a renewed interest in former dark ages. It is never permanent, and we shouldn't take it too seriously."
One paradigm or narrative will hold sway for awhile until someone comes along who wants to prove their intellectual bonafides by upsetting the applecart and overturning the accepted narrative.
The pendulum swings one way, then the other, hopefully going to less of an extreme each time, until a better, more accurate picture of the past emerges.
Or at least the most egregious errors and ideological agendas are purged.
I was going to go with a list, starting with peripheral causes and then zeroing in on the biggie, but the biggie is so big it cascades over into all the others, so it makes sense to start with the main cause and expand outward from that.
The Roman Leviathan, which dominated the Mediterranean for centuries, essentially fell because it was subjected to more stress than the system could absorb. The empire was an organization, a kind of information system. If you disrupt a system enough, introduce enough chaos, it will eventually reach a tipping point and dissolve.
So what were the primary sources of stress?
Here's my Quick Start Guide to the Fall of the Roman Empire.
1) Barbarian invasions
This is a controversial thing to say these days, as the current trends is to absolve the negative impact of barbarian attack ('migration'). Damage inflicted by barbarians is downgraded or simply ignored by the hip historians, leaving it to the fuddy duddy's to hold their feet to the fire.
Hipster historians are willing to write off the 40 million people killed, for example, during the campaigns of Genghis Khan as insignificant. Because trade routes and culture exchange! They're trying to offset the previous focus on Mongol city razing and balance the account, but they're swinging the pendulum too far in his case.
Of course, Genghis arrives on the scene long after Rome succumbed, but he's nevertheless part of the same phenomenon: the collision of vast, wealthy, and well-established agrarian states and mobile, poor, yet militarily superior steppe peoples.
Barbarians were always at the borders of Rome. That's very true. But the pressure they exerted increased greatly over time, and escalated from footmen to mounted archers. Areas that had been quiet, such as North Africa, also became more active threats over time.
During the Classical period, the legions of Rome dominated the region with their professionalism and highly flexible formations. Armed with a short sword (gladius) and throwing spear (plum), they were better organized and frequently better led than those of their opponents around the Mediterranean basin.
And they were almost all foot soldiers.
Fortunately, their opponent's armies were composed, primarily, of footmen as well. Cavalry were expensive to field. When the proportion of cavalry eventually increased, they frequently weren't Romans at all, but hired barbarian mercenaries.
Nomadic peoples of the steppes began to impact the borders of the Roman during the third century AD, which was a calamitous period for Rome thanks to a mixture of invasions, revolts, plagues, civil war, economic depression, currency debasement, and secession. Rome went through 20 emperors in 50 years. It brought the Mediterranean Leviathan to the brink of collapse.
The arrival of the Goths complicated things further, and it would get worse when the Vandals and Huns showed up.
Why? Agrarian based states at this time were unable to effectively counter the masses of horse archers that nomads deployed. This was true for all the states bordering upon the steppes: China, Persia, India, and Rome all experienced devastation at the hands of mounted invaders.
Settled civilizations had to adapt to an enemy that could literally ride circles around them. That or perish.
Both China and Rome, the two most easily accessible from the steppes, tried bribery. China was expert at playing on nomad people off against another, and did so with aplomb for centuries. Rome hired barbarians to provide cavalry forces for their armies, until, eventually, the barbarians essentially became the Roman army. But they were never accepted as Romans. Just foxes guarding the hen house.
Rome's riches were extremely tempting to poor steppe peoples who didn't have the food surpluses necessary to support as much specialized labour.
Given how easily settled states could be crushed militarily, it made sense for the nomads to prey upon them and extort vast tributes.
2) Military inferiority
The legions built an empire for Rome, and for hundreds of years, nothing could stand against them. But by the third century, things had changed. The legions found themselves outclassed by new, mounted opponents.
In addition, the population of Germany had increased, and with it pressure against the borders of the empire, so there would have been some increase in military spending to meet the rising tide regardless of whether or not the steppe peoples arrived.
But horse archers were much more dangerous than the axe wielding barbarians Romans were used to: the hordes were the equivalent of Classical Era Panzer Divisions, practicing early Blitzkrieg.
Foot soldiers simply couldn't keep up, nor could they force a faster moving enemy to battle. Mounted troops would ride up, fire an arrow from their powerful composite bow, and retreat out of range before defenders could respond.
It is not known if the Huns brought stirrups to Europe. It's within the realm of possibility, but just their mobility and composite bow was enough to give them a decisive edge. In fact, the horse archer dominated the world militarily until rifles were developed. Only then could foot soldiers cut down mounted troops before they had a chance to loose their arrows.
Obviously the first two points (barbarian invasion and military inferiority) are intertwined. The fact that China and Rome could not beat the nomads mano a mano meant they had to co-opt, bribe, or hire nomads to fight for them. China, which had a much larger population and was, relatively speaking, more culturally powerful and homogenous than Rome, was better able to absorb invaders than its polyglot Roman counterpart, and did so repeatedly. Barbarians would conquer China only to become Chinese.
3) Increasing internal oppression and erosion of rights and security
In order to deal with the inability of Roman forces to hold the enemy at the border, whole regions were abandoned by civilians, who understandably did not want to be casually raped and pillaged by raiders.
The change was noticed: Emperor Diocletian saw that the empire was caving under barbarian pressure and implemented sweeping military and civil reforms.
First he divided the military into two branches: a limited, fortified, stationary border guard to sound the alarm and hold back small incursions, and elite mobile legions held in the rear to deal with major invasions. These would ride out to meet enemies who penetrated deep into Roman territory. It was now defense in depth, the same defensive tactic adapted to thwart Blitzkrieg during the Second World War.
The idea of holding barbarians right at the border was a thing of the past. Front lines were too brittle.
Yet Rome was already spending half its budget on the military (the United States spends roughly 20%). This not only increased, but in order to secure a stable supply system for the military, Diocletian forced people to remain in place, forbidding them from moving, as well as forcing male children to take up the vocation of their father.
Anyone unfortunate enough to live in a border territory was now stuck there.
Yet this way Diocletian could guarantee that the supply system for the army wouldn't erode or collapse as people decided to move or switch professions.
It unquestionably made the Roman Empire a worse place to live. Only a very small, rich minority would have been unaffected.
The reason for these changes? Pressure from barbarians. Without that pressure, there would be no reason for such drastic changes to the circumstances under which the civilian population lived.
Diocletian also brought in a system of guilds, to which workers were compelled to belong.
The predation by barbarians changed everything and resulted in the militarization of an entire society.
Rome was now a military with a state, rather than a state fielding a military. This kept the empire humming along for another century or two. From Diocletian's harsh reforms to the final collapse of the (Western) Roman Empire, we are looking at an interstitial period, Late Antiquity, that bridges the gap between the Classical Era and Medieval Feudalism (and The Dark Ages, if you believe they happened at all). The knights of the feudal era, and the peasants who supported them, are a response to the threat of mounted troops.
One thing you will find over and over again throughout history: trade increases wealth, so savvy leaders protect merchants and trade routes, because they generate wealth, and wealth can be taxed.
As the Roman state could no longer guarantee the security of merchants, long distance trade declined. Drastically. The payoff was no longer justified given the increased risks involved.
And so the state and everyone in it became poorer.
It had already been through a major depression during the Crisis of the Third Century, and Roman currency had been badly debased. Diocletian tried to rectify this with strict price controls and draconian punishments, but they didn't work and didn't last.
4) Lack of a peaceful means of succession and state fragmentation
Democracy allows for the peaceful transition of power, and it's one tool the Romans didn't have.
When an emperor died, every ambitious noble and power hungry general scrambled for the diadem.
This handy chart from Randal S. Olson's site shows length of reign and means of death for emperors between 27 BC and 395 AD:
Emperors were often assassinated by their successor. Sometimes this impacted just the emperor and his immediate family (all would be hunted down and murdered), other times it devolved into civil wars that would convulse the state and disrupt trade for a year or two. Armies would be stripped away from the frontier to fight for the Imperial Purple, allowing barbarians to flood into Roman territory unhindered.
Over time, any highly coveted position will see the investment contenders make to seize it increase, until, eventually, the investment made far outweighs the actual benefit of the position itself.
This is very much the case with the Imperial Throne. After moving Heaven and earth to gain the it, many emperors perished within a year or two, murdered by the next in line. It was like a revolving door.
The actual benefit of the position declined precipitously. Power began to be wielded more by people behind the scenes, as sitting on the throne was simply too dangerous. The last emperors were little more than puppets of barbarian power brokers holding the position of the Magister Militum, head of the (now not so) Roman Army. Eventually the barbarian generals decided to do away with the figurehead emperor entirely.
Many governors, if they couldn't take the throne, seceded from the Empire and established their own, separate domain where they could be numero uno. Britain, for example, was a separate domain for years, first as part of the Gallic Empire (259-274 AD) and then as the Britannic Empire (286-296 AD) until finally being brought to heel.
This sort of secession was so common that Diocletian separated military and civil powers to prevent any one man from holding too much power. Diocletian even divided rule of the empire between four Tetrarchs.
Then he retired to raise cabbages.
It wasn't enough.
Despite all of Diocletian's efforts, the Romans preferred fighting amongst themselves when they should have been dealing with invaders. Internal competition led to alliances with external enemies that further damaged the state.
Over time, the invaders of China became Chinese. This didn't happen with Rome, which was incapable of assimilating the barbarians. Indeed, the Romans resisted making Germans, in particular, into Roman citizens, to their own detriment. Emperor Honorius indulged his prejudice against them and had the families of the Goths, some 30,000 women and children, who were under Roman protection at the time, murdered.
Not a good way to co-opt people.
6) Slavery and wealth polarization
The rich got richer and the common free man got poorer as the empire aged.
Slavery only benefits a small minority at the top of the totem pole. Vast slave estates made it impossible for free men to compete as farmers, and eventually the free men were driven into debt or fled to Rome to live on the dole. Others took shelter under rich lords, accepting their protection from debt collectors in exchange for labour.
It was the beginning of serfdom.
It had become much harder for the little people to make a living. Whatever middle class had existed was being squeezed out of existence as the rich pressed their advantage and impoverished everyone else.
Enormously wealthy senators didn't pay taxes and were exempt from military service, into which ordinary people could find themselves unceremoniously dragooned.
There was no Solon to strike a balance between the interests of the rich and the poor. The system had degenerated too far and become too corrupt. What few protections there were for the average citizen had been eroded away, and they had less and less reason to be loyal to the state that oppressed them in the name of protecting them.
From the point of view of the elite, there was little reason for technological innovation, as slaves (human beings) are incredibly sophisticated machines, capable of a wide range of functions. Disposable people made automation irrelevant and held back the development of practical, labour saving devices.
The ancients knew of all sorts of things, of course, including steam power. They just didn't see any economic reason to harness such marvels, except as toys or for spectacle. It was far cheaper to use people.
When the Roman state collapsed, the barbarians kept some elements of the bureaucracy functioning. The rich certainly faired better than the poor, and the senate continued to meet. Some of them cooperated with their new, barbarian overlords while others fled to Constantinople.
But eventually all of the state systems that Rome had built withered away. The remarkable Roman roads became overgrown. Long distance trade dried up. Aqueducts, stadiums, and magnificent baths slowly collapsed and no one knew how to rebuild them.
The forum, centre of life in Rome, became a cow pasture.
That's my top six. Other possible factors:
The Roman Empire was hit repeatedly by massive plagues, and some of the worst occurred during its later years, such as the Plague of Justinian. That one, of course, was too late to account for Rome's collapse, just as the Antonine Plague was too early.
No doubt there were others, and they may have impacted the ability of the empire to defend itself.
As was seen in the collapse of the Incan and Aztec Empires, disease can devastate not only the military forces of a state (indeed, large concentration soldiers were breeding grounds for disease, including The Spanish Flu), but the bureaucracy and supply systems behind it, making the government incapable of defending the state and its people effectively.
But I'm really speculating with this one. The barbarians would have been affected by plague as well. When Pope Leo I turned back Attila from the gates of Rome, some say it was less because of God and gold and more because plague had broken out in the Hun camps.
8) Climate change
Areas in North Africa were already abandoned and left fallow before barbarians overran them, suggesting that they were already no longer economically viable. Food production declined. There is evidence that life in general had become more difficult.
A change in climate, possibly a mini-ice age, might explain this.
Rise and Fall
The animation below shows the expansion and contraction of the empire from the time of the republic:
Lead poisoning may have reduced the effectiveness of the ruling elite and driven some of them mad, but I'm not sure how major a factor that really was. Christianity was militarized by Constantine, so its earlier pacifist, slave ideology origins were successfully co-opted by the state and seem an unlikely cause of its collapse. It did cause instability for a time as various factions competed for dominance.
Rome hit a high with Marcus Aurelius and the golden age of the second century, got slammed in the third, was saved by Diocletian's reforms, which helped it trudge through the fourth, but then got finally overwhelmed in the fifth.
Acting together the top six points created a perfect storm.
The Eastern Roman Empire, however, would continue to exist until Constantinople fell in 1453.